1. Technical Field of the Invention
The present invention relates to a gravure coating apparatus for coating uniformly a coating solution on a surface of a support continuously conveyed.
2. Description of the Related Art
A gravure coating apparatus has been known as an apparatus for coating a coating solution on a surface of a flexible strip support. In the gravure coating apparatus, as shown in FIG. 3, a gravure roll 1 rotationally driven in the direction shown by the arrow A is immersed in a liquid pool 2a, which is a recession formed in a manifold block 2 while maintaining a certain distance to the outer peripheral surface of the gravure roll 1, whereby the coating solution L is applied to the outer peripheral surface of the gravure roll 1. Thereafter, as shown in FIG. 4, the coating solution L held in cells carved on the outer peripheral surface of the gravure roll 1 is transferred and coated on a flexible strip support 5, while a redundant part of the coating solution L coated on the outer peripheral surface of the gravure roll 1 is scraped off with a doctor blade 4, which is pressed onto the outer peripheral surface of the gravure, roll 1 (as described, for example, in JP-U-4-41764).
The coating solution L thus coated on the outer peripheral surface of the gravure roll 1 and then scraped off with the doctor blade 4 is collected to a recovery pan 6 through an outer surface 2c of a part 2b where the outer peripheral surface of the gravure roll moves out of the manifold block 2.
In the gravure coating apparatus of this kind, as shown in FIG. 5, the redundant coating solution recovered by scraping off with the doctor blade 4 with a relatively large length forms a number of fluxes Ls in longitudinal stripe form due to contraction flows with small distances in the transversal direction caused by action of surface tension. The fluxes Ls in longitudinal stripe form make unevenness in pressure of the coating solution onto the back surface of the tip end part of the blade, which causes unevenness in amount of the coating solution passing through the doctor blade 4, whereby the transferred and coated amount of the coating solution on the surface of the flexible strip support 5 is disproportionated in the transversal direction.
In order to prevent the problem, it has been practiced such a measure as shown in FIG. 6 that a curved coating solution guide 7 is provided on the manifold block 2 on the side where the outer peripheral surface of the gravure roll moves out, while maintaining a certain distance with the outer peripheral surface of the gravure roll 1, and the tip end part of the coating solution guide 7 is extended to a position immediately near the contact point of the doctor blade 4 and the gravure roll 1, whereby the fluxes Ls in longitudinal stripe form of the coating solution L thus scraped off and recovered with the doctor blade 4 are prevented from influencing on the transferred and coated amount of the coating solution L (as described, for example, in JP-A-63-194766).
However, in the case where the coating solution guide 7 is extended to a position immediately near the contact point of the doctor blade 4 and the gravure roll 1 for suppressing the fluxes Ls in longitudinal stripe form of the recovered coating solution L from occurring, the liquid pressure and the liquid resistance of the coating solution L passing through the coating solution guide 7 are increased when the coating solution L has a high viscosity, and as a result, there is such a possibility that the transferred and coated amount of the coating solution L on the flexible strip support 5 becomes uneven due to deformation of the doctor blade 4. When the coating solution L passing through the coating solution guide 7 has a low viscosity, furthermore, there is such a possibility that the coating solution L is not favorably charged in the gap between the outer peripheral surface of the gravure roll 1 and the coating solution guide 7. Moreover, there may be problems in workability, cleanability, detaching operationality and maintenancability of the coating solution guide 7 depending on the shape thereof.